The "modulate" ColorMode was the default in 0.8.0, and its functionality (multiplying the current color with the texture) is still the default in 0.9.0.
The effects of the "replace" ColorMode can be duplicated by calling love.graphics.setColor(255, 255, 255).

The "combine" ColorMode can be duplicated via a pixel shader. The shader code would look something like this: